Some (like myself) tend to "rag" on D44's because their strength is barely above that of the axle that comes stock (and to get it well above that using aftermarket upgrades starts costing what bigger & better axles would cost).
I s'pose you might already know my opinion, but I would say unless you want to go full width, consider keeping what you have. It's a good sturdy axle (possibly aside from the locking hubs... throw a set of Jeep hubs on it, then no worries there). There's a lot of tech available here for making the stock suspension setup perform as well.
If fullwidth IS what you're after, then look for the '79down F-150 axles (for SAS). Your stock driveshaft can work (will need either a conversion u-joint, or the yoke on the D44 swapped to a 1310-size), but it may need to be shortened slightly unless you push the axle forward at least 1½"-2".
